This invention relates to backrests for chairs. More particularly, the invention relates to a backrest that provides adjustable support to the lumbar region of the back of a user seated on a chair.
Backrests that provide lumbar support are known. The majority of these backrests have a non-adjustable lumbar support. The lumbar support is built into the back rest and is therefore configured to provide adequate support for a typical person. In practice, such backrests provide inadequate support for people who are larger or smaller than average. Adjustable lumbar supports are also known, however, these devices tend to have complex adjustment mechanisms that are both heavy and costly.
For example, Kemmann describes an adjustable backrest in U.S. Pat. No. 4,810,033. This backrest has an outer frame that holds a deformable plate that provides lumbar support. The top portion of the plate (i.e. the region of the plate nearer the upper back of a user) is formed into a series of longitudinal slats, running from the top of the lumbar support to its centre. The lower portion of the lumbar support plate (i.e. the portion which actually supports the user""s back) does not have any openings and is less flexible. A control knob is drivingly connected to the plate through a complex mechanism and is rotatably mounted to change the position of the lower portion of the plate to force the plate outwardly to whereby the plate provides lumbar support.
One disadvantage of lumbar adjustment mechanisms is that they utilize complex and costly adjustment mechanisms. Therefore, they tend to be provided on more expensive chairs. Thus they may be provided on chairs for executives and professionals but not an secretarial chairs who would also benefit from a more ergonomic chair. Further, due to the complexity of the mechanism, the mechanism is prone to breaking.
In accordance with one aspect of the instant invention, there is provided a backrest for supporting a person""s back having a front surface and a rear surface, the backrest comprising a flexible support section having a fixed end which is mounted to a support structure and a free end which is displaceable vertically with respect to the fixed end, the support section is configured to be compressed and displaced forwardly when the free end is moved towards the fixed end; an adjustment member drivingly connected to the free end; and a detent member for selectively receiving the adjustment member in one of a plurality of positions, the support member biasing the adjustment member into retaining engagement with the detent member due to the compression of the flexible support member by the displacement of the free end towards the fixed end. This provides a simple, reliable mechanical adjustment member for a back rest of a chair and, preferably for the lumbar support member of a back rest.
In one embodiment, the support structure comprises a frame and a shell mounted on the frame and the support section is provided as part of the shell.
In another embodiment, the frame has an opening sized to receive therein the support section.
In another embodiment, the support member comprises a plurality of slats extending vertically between the fixed end and the free end of the support section.
In another embodiment, the slats extend from a position adjacent the fixed end to a position adjacent the free end.
In another embodiment, the shell comprises a perimeter section surrounding a central section in which the support structure is provided and, when mounted on a chair, the support structure has a vertical extent sufficient to support at least the lumbar region of the person when seated in the chair.
In another embodiment, the shell has first engagement members and the frame has second engagement members configured to engage the first engagement members whereby the engagement of the first and second engagement members retains the shell on the frame.
In another embodiment, one of the first engagement members and the second engagement members comprise a plurality of openings and the other of the first and second engagement members comprises projecting members that are locking received in the openings.
In another embodiment, the fixed end comprises the upper end and the free end comprises the lower end and the detent member comprise a plurality of vertically spaced apart members each of which has a downwardly extending recess and the adjustment member is sized to be received in each recess.
In another embodiment, the detent member comprises a plurality of vertically spaced apart members each of which has a recess to receive therein the adjustment member and support member biases the adjustment member into engagement with the recesses.
In another embodiment, the frame has a front face and a vertically extending opening adjacent the free end, the shell is mounted on the front face, the adjustment member is mounted at the free end of the support structure and has a handle which extends through the vertically extending opening whereby the support structure may be actuated from the rear of the backrest.
In accordance with another aspect of the instant invention, there is provided a backrest for supporting a user""s back having a front surface and a rear surface, the backrest comprising a frame; a shell mounted on the frame, the shell having a flexible support section; and first engagement members provided an the shell and second engagement members provided on the frame, the second engagement members are configured to engage the first engagement members whereby the engagement of the first and second engagement members retains the shell on the frame. This construction provides a simple and easily manufacturable flexible back rest for a chair.
In accordance with another aspect of the instant invention, there is provided a backrest a backrest for supporting a user""s back having a front surface and a rear surface, the backrest comprising a shell having a perimeter section surrounding a central section and a plurality of slats extending vertically between the perimeter to occupy the central section and, when mounted on a chair, the slats have a vertical extent sufficient to support at least the lumbar and mid back regions of the person when seated in the chair; a frame having an opening sized to receive therein the slats; and mounting members to mount the shell on the frame. This construction provides a simple and easily manufacturable flexible back rest for a chair.